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Theme 3 - 104 > Drugs Affecting the Kidneys (L6) > Flashcards

Drugs Affecting the Kidneys (L6) Flashcards

1
Q

What are diuretics?

A

A compound that causes the excretion of an increased volume of urine of the body (more water and solutes excreted)

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2
Q

What is natriuresis?

A

The increased excretion of Na+

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3
Q

What is kaliuresis?

A

The increased excretion of K+

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4
Q

How do diuretics increase water and Na+ excretion?

A
  • They reduce reabsorption of Na+ from the filtrate

- This leads to more water being lost also

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5
Q

What is an aquaretic diuretic?

A

A diuretic that increases urine excretion without increasing Na+ excretion

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6
Q

What are the main uses of diuretics?

A
  • To reduce circulating fluid volume

- To remove excess body fluid (oedema)

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7
Q

What are the classes of diuretic agents?

A
  • Carbonic anhydrase inhibitors
  • Osmotic diuretics
  • Loop diuretics
  • Thiazides and Thiazide-likes
  • Potassium-sparing diuretics
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8
Q

How do loop diuretics work?

A
  • Inhibits NKCC2 transporters in the thick ascending limb of the loop of Henle
  • This leads to a reduced intake of Na+, K+ and Cl-
  • Therefore, more water gets exerted (increased urine volume)
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9
Q

Methods of loop diuretic administration

A
  • Oral absorption which leads to diuresis in 1 hour and lasts for 4-6 hours
  • IV administration which leas to diuresis in 5 minutes and lasts for 2 hours
  • Intramuscular (IM) administration (injection into the muscle) which starts diuresis in 30 minutes
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10
Q

Unwanted effects of loop Diuretics

A
  • Dehydration
  • Hypokalaemia
  • Metabolic alkalosis (due to loss of H+ to urine
  • Deafness
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11
Q

What can loop diuretics be used for?

A
  • Acute pulmonary oedema
  • Chronic heart failure
  • Liver cirrhosis
  • Resistant hypertension
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12
Q

How do loop diuretics cause hypokalaemia?

A
  • Because loop diuretics inhibit the NKCC2 inhibitors in the thick ascending limb of he loop of Henle, more Na+ recaches the DT
  • This leads to an increased Na+ intake via Na+/K+ATPase which gets exchanged for K+
  • Therefore there is an increased K+ loss
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13
Q

How do thiazides work?

A

Act on the DT and inhibit the apical Na+/Cl- co-transporter, leading to Na+ excretion and therefore increased water excretion. They are not as powerful as loop diuretics.

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14
Q

Examples of thiazides

A
  • Bendrofluazide (treats mild heart failure)

- Inadapamide (can treat hypertension)

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15
Q

What can thiazides be used to treat?

A
  • Hypertension
  • Oedema
  • Mild heart failure
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16
Q

Unwanted effects of thiazides

A
  • Hypokalaemia
  • Metabolic alkalosis (due to H+ loss to urine)
  • Increased uric acid in plasma
  • Hyperglycaemia
  • Increased plasma cholesterol
  • Male impotence
17
Q

Why is Indapamide preferred over Bendrofluazide?

A

Because it has fewer unwanted effects

18
Q

What can mild hypokalaemia lead to?

A
  • Fatigue
  • Drowsiness
  • Dizziness
  • Muscle weakness
19
Q

What can sever hypokalaemia lead to?

A
  • Abnormal heart rhythm
  • Muscle paralysis
  • Death
20
Q

What are potassium-sparing diuretics?

A
  • Diuretics that do not lead to hypokalaemia
  • They do so by acting on the DT to inhibit Na + reabsorption and K+ doesn’t get secreted into the DT
  • They are less effective than thiazides and loop diuretics
21
Q

What are the two types of potassium-sparing diuretics?

A
  • Aldosterone antagonists (e.g. eplerenone and spironolactone)
  • Non-aldosterone antagonists (e.g. amiloride and triamterene)
22
Q

How does Spironolactone work?

A
  • Spironolactone get metabolised to canrenone, a competitive antagonist of aldosterone
  • This reduces Na+ reabsorption from the DT because less Na+ channels will be expressed
  • It is less effective than eplerenone
23
Q

Unwanted effects of Spironolactone

A
  • Hyperkalaemia
  • Metabolic acidosis
  • GI upsets
24
Q

What can Spironolactone treat?

A
  • Heart failure

- Oedema

25
Q

How do non-aldosterone antagonists work?

A
  • Act on DT by inhibiting Na+ reabsorption and decreasing K+ excretion
  • It does this by blocking luminal Na+ channels, where aldosterone has its main effects produced
26
Q

What can potassium-depleting diuretics (e.g. thiazides and loop diuretics) be given with to limit hypokalaemia?

A

Potassium-sparing diuretics

27
Q

Why are some diuretic drugs given in combination with other diuretic drugs?

A
  • To increase diuretic effect because some patients may not respond well to a certain type of diuretic
  • To prevent hypokalaemia
28
Q

Describe carbonic anhydrase inhibitors

A
  • Block the reabsorption of NaHCO3 in the PT
  • Not used as a diuretic because it only causes weak diuresis
  • One of the earliest diuretics produced
29
Q

What can carbonic anhydrase inhibitors treat?

A
  • Glaucoma

- Epilepsy

30
Q

Why is water a diuretic agent?

A
  • High volumes of water intake leads to less ADH being secreted
  • Therefore, less AQP2 channels are expressed in the late DT and early collecting duct
  • So more water gets excreted

Theme 3 - 104 (3 decks)

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